1. Field of the Invention
This invention relates to a support structure for a bicycle saddle. It more particularly relates to a saddle support structure which allows simultaneous positional adjustment of the saddle in the directions of the height and length of the bicycle to enable the cyclist to assume an optimum riding posture depending on running conditions.
2. Description of the Prior Art
Typically, a bicycle saddle is supported on a seat post which is inserted into and fixed to the seat pipe of the bicycle frame. The upper end of the seat pipe has a longitudinal cutout which is bounded by a pair of flanges or clips which are penetrated by a clamping or clipping bolt. Tightening and loosening of the clip bolt causes the clips to move toward and away from each other, thereby diametrically contracting and expanding the seat pipe upper end to lock and unlock the seat post. Thus, the saddle may be adjusted in vertical position by sliding thereof relative to the seat pipe when the clip bolt is loosened.
Generally, the seat pipe of the bicycle frame extends obliquely upward and rearward. Therefore, height adjustment of the saddle inevitably results in displacement thereof lengthwise of the bicycle. For example, the saddle is displaced rearwardly of the bicycle when it is adjusted to a higher position. Such a manner of saddle position adjustment is acceptable in most cases because a cyclist having long legs also has correspondingly long arms and therefore prefers a higher saddle position with the saddle located farther from the handlebar.
In special bicycles such as mountain bicycles or motocross bicycles (BMX bicycles), it is often required for the cyclist to assume various riding postures depending on the running conditions. For example, when running in an upward slope, the cyclist tries to bring his (or her) weight center upwardly and forwardly to produce a larger pedalling force, thus desiring a higher and forward saddle position. When running in an downward slope, on the other hand, the cyclist endeavors to shift the body weight center downward and rearward to ensure a higher running stability, consequently requiring a lower and rearward saddle position.
With the typical prior art saddle support structure, however, the saddle can be raised only with resultant rearward displacement thereof, and lowered only with forward shifting. Such shifting of the saddle lengthwise of the bicycle is quite against the requirements for mountain bicycles or BMX bicycles. Therefore, the cyclist must assume riding postures to meet various running conditions irrespective of the actual saddle position.
Japanese Utility Model Application Laid-open No. 59-64383 (Laid-open: April 27, 1984; Application No.: 57-160,114; Filed: October 22, 1982; Inventor and Applicant: Kazuo MURASAKI) discloses a bicycle saddle support structure which provides remote control adjustment of the saddle position. More specifically, this saddle support structure comprises a seat post slidably fitted in the seat pipe of the bicycle frame, and a compression coil spring accommodated within the seat pipe to upwardly urge the seat post from below. The seat post is formed on its cylindrical outer surface with engaging grooves, while the seat pipe is provided at its upper end with an annular engaging member. The engaging member is variable in diameter by operating a remote control lever for engagement with and disengagement from any one of the engaging grooves. The seat post becomes slidable relative to the seat pipe when the engaging member is disengaged from a particular engaging groove. The compression coil spring always urges the seat post upward, so that the saddle position can be adjusted simply by raising or lowering the cyclist's hips and subsequently bringing the engaging member into engagement with another engaging groove.
The saddle support structure of the above laid-open Japanese utility model application allows the cyclist to adjust the saddle position during riding. However, since the seat post is slidably guided by the bicycle frame seat pipe which extends upwardly rearward, height adjustment of the saddle results in undesirable shifting thereof lengthwise of the bicycle at least with respect to mountain bicycles or BMX bicycles, as hereinbefore described.